Static random access memory (SRAM) is commonly used in integrated circuits. SRAM cells have the advantageous feature of holding data without a need for refreshing. SRAM cells may include different numbers of transistors, and are often accordingly referred to by the number of transistors, for example, six-transistor (6-T) SRAM, eight-transistor (8-T) SRAM, and the like. The transistors typically form a data latch for storing a bit. Additional transistors may be added to control the access to the transistors. SRAM cells are typically arranged as an array having rows and columns. Typically, each row of the SRAM cells is connected to a word-line, which determines whether the current SRAM cell is selected or not. Each column of the SRAM cells is connected to a bit-line (or a pair of bit-lines), which is used for storing a bit into, or read from, the SRAM cell.
For the multi-bank design of SRAM memories, long global bit-lines are used to connect columns of banks. FIG. 1 illustrates a portion of a column of a SRAM memory including multiple banks. Global bit-lines 2 (which may form a differential pair) connect global read/write circuit 4 to the banks in the column. In each of the banks, local bit-lines 6 interconnect the SRAM cells inside the respective bank. In a write operation, global read/write circuit 4 generates a full-swing signal and places the signal on global bit-lines 2. With the full-swing signal, one of the global bit-lines 2 has a voltage of VDD, while the other has the voltage of VSS. Write driver 10 receives the full-swing signal from global bit-lines 2, and writes a full-swing signal to local bit-lines 6. In a read operation, read sense amplifier 8 reads a signal from local bit-lines 6, amplifies the signal, and sends the amplified signal to global read/write circuit 4.
The conventional SRAM circuit suffers from drawbacks. During the write operations, writing full-swing signals to global bit-lines 2 is time consuming, particularly when global bit-lines 2 are long. Further, since the writing involves the charging of capacitors, it is also power consuming. A solution is thus needed to solve the above-discussed problems.